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it will be found that the acuteness of smell bears a proportion in all animals to the extent of surface which this membrane displays; and hence, in the dog and cattle tribes, as well as in several others, it possesses a variety of folds or convolutions, and in birds is continued to the utmost points of the nostrils, which in different kinds open in very different parts of the mandible.
The frontal sinuses, which are lined with this delicate membrane, are larger in the elephant than in any other quadruped, and in this animal the sense is also continued through the flexible organ of its proboscis. In the pig the smelling organ is likewise very extensive and in most of the mammals possessing proper horns it ascends as high as the processes of the frontal bone from which the horns issue.
It is not known that the cetaceous tribes possess any organ of smell; their blowing-holes are generally regarded as such; but the point has been by no means fully established. We are in the same uncertainty in respect to amphibials and worms; the sense is suspected to exist in all the former, and in several of the latter, especially in the cuttle-fish, but no distinct organ has hitherto been traced out satisfactorily.
In fishes there is no doubt; the olfactory nerves are very obviously distributed on an olfactory membrane, and in several instances the snouts are double, and consequently the nostrils quadruple, a pair for each snout. This powerful inlet of pleasure to fishes often proves fatal to them from its very perfection; for several kinds are so strongly allured by the odour of marjorum, assafoetida, and other aromas, that by smearing the hand over with these substances, and immersing it in the water, they will often flock towards the fingers, and in their intoxication of delight may easily be laid hold of. And hence the angler frequently overspreads his baits with the same substances, and thus arms himself with a double decoy.
There can be no doubt of the existence of the same sense in insects, for they possess a very obvious power of distinguishing the odorous properties of bodies, even at a considerable distance beyond the range of their vision but the organ in which this sense resides has not been satisfactorily pointed out; Reimar supposes it to exist in their stigmata, and Knoch in their anterior pair of feelers.
The general organ of HEARING is the ear, but not always so; for in most of those who hear by the Eustachian tube only, it is the mouth, and in the whale tribes the nostrils or blow-hole. It is so, however, in all the more perfect animals, which usually for this purpose possess two distinct entrances into the organ, a larger and external, surrounded by a lobe; and a smaller and internal, opening into the mouth. It is this last which is denominated the Eustachian tube. The shape of the lobe is seldom found even in mammals similar to that in man, excepting among the monkey and the porcupine tribes. In many kinds there is neither external lobe nor external passage. Thus, in the frog, and most amphibious animals, the only entrance is the internal, or that from the mouth; and in the cetaceous tribes the only effective entrance is probably of the same kind; for, though these may be said to possess an external aperture, it is almost im perceptibly minute. It is a curious fact, that, among the serpents, the blind-worm or common harmless snake is the only species that appears to possess an aperture of either sort; the rest have a rudiment of the organ within, but we are not acquainted with its being pervious to sound.
Fishes are well known to possess a hearing organ, and the skate and shark have the rudiment of an external ear; but, like other fishes, they seem chiefly to receive sound by the internal tubule alone.
That insects in general hear is unquestionable, but it is highly question. able by what organ they obtain the sense of hearing. The antennas, and perhaps merely because we do not know their exact use, have been supposed by many naturalists to furnish the means; it appears fatal, however, to this opinion to observe, that spiders hear though they have no true antennas, and that other insects which possess them naturally seem to hear as correctly after they are cut off.
The sense of VISION exhibits perhaps more variety in the different classes of animals than any of the external senses. In man, and the greater number of quadrupeds, it is guarded by an upper and lower eye-lid; both of which in man, but neither of which in most quadrupeds, are terminated by the additional defence and ornament of cilia or eye-lashes. In the elephant, opossum, seal, cat kind, and various other mammals, all birds, and all fishes, we find a third eye-lid, or nictitating membrane, as it is usually called, arising from the internal angle of the eye, and capable of covering the pupil with a thin transparent veil, either wholly or in part, and hence of defending the eyes from danger in their search after food. In the dog this membrane is narrow; in oxen and horses it will extend over half the eyeball; in birds it will easily cover the whole; and it is by means of this veil, according to Cuvier, that the eagle is capable of looking directly against the noon-day sun. In fishes it is almost always upon the stretch, as in their uncertain element they are exposed to more dangers than any other animal. Serpents have neither this nor any other eye-lid: nor any kind of external defence whatever but the common integument of the skin.
The largest eyes in proportion to the size of the animal belong to the bird tribes, and nearly the smallest to the whale; the smallest altogether to the shrew and mole; in the latter of which the eye is not larger than a pin's head.
The iris, with but few exceptions, partakes of the colour of the hair, and is hence perpetually varying in different species of the same genus. The pupil exhibits a very considerable, though not an equal variety in its shape. In man it is circular; in the lion, tiger, and indeed all the cat kind, it is oblong; transverse in the horse and in ruminating animals ; and heart-shaped in the dolphin.
In man, and the monkey tribes, the eyes are placed directly under the forehead; in other mammals, birds, and reptiles, more or less laterally; in some fishes, as the genus pleuronectes, including the turbot and flounder tribes, both eyes are placed on the same side of the head; in the snail they are situated on its horns, if the black points on the extremities of the horns of this worm be real eyes, of which, however, there is some doubt: in spiders the eyes are distributed over different parts of the body, and in different arrangements, usually eight in number, and never less than six. The eyes of the sepia have lately been detected by M. Cuvier; their construction is very beautiful, and nearly as complicated as that of vertebrated animals.* Polypes and several other zoophytes appear sensible of the presence of light, and yet have no eyes; as the nostrils are not in every animal necessary to the sense of smell, the tongue to that of taste, or the ears to that of sound. A distinct organ is not always requisite for a distinct sense. In man himself we have already seen this in regard to the sense of touch, which exists both locally and generally; the distinct organ of touch is the tips of the tongue and of the fingers, but the feeling is also
* Le Regne Animale distribue d'apres son Organization, 4 tomes, 8vo. Paris 1817.
diffused, though in a subordinate and less precise degree, over every part of the body. It is possible, therefore, in animals that appear endowed with particular senses without particular organs for their residence, that these senses are diffused, like that of touch, over the surface generally; though there can be no doubt, that, for want of such appropriate organs, they must be less acute and precise than in animals that possess them.*
But who of us can say what is possible? who of us can say what has actually been done? After all the assiduity with which this attractive science has been studied, from the time of Aristotle to that of Lucretius, or of Pliny, and from these periods to the present day,-after all the wonderful and important discoveries which have been developed in it, natural history is even yet but little more than in its infancy, and zoonomy is scarcely entitled to the name of a science in any sense. New varieties and species, and even kinds of beings, are still arising to our view among animals, among vegetables, among minerals :-new structures are detecting in those already known, and new laws in the application of their respective powers.
But the globe has been upturned from its foundation; and with the wreck of a great part of its substance has intermingled the wreck of a great part of its inhabitants. It is a most extraordinary fact, that of the five or six distinct layers or strata of which the solid crust of the earth is found to consist, so far as it has ever been dug into, the lowermost or granitic, as we observed on a former occasion,† contains not a particle of animal or vegetable materials of any kind; the second, or transition formation, as Werner has denominated it, is filled, indeed, with fossil relics of animals, but of animals not one of which is to be traced in a living state in the present day; and it is not till we ascend to the third, or floetz stratification, that we meet with a single organic remain of known animal structures.
M. Cuvier has been engaged for the last fifteen years in forming a classification, and establishing a museum of nondescript animal fossils, for the purpose of deciding, as far as may be, the general nature and proportion of those tribes that are now lost to the world: and in the department of quadrupeds alone, his collection of unknown species amounted in the year 1810 to not less than seventy-eight, some of which he has been obliged to arrange under new genera, as we shall have occasion to notice still further in a subsequent study. In the new and untried soil of America, the bones of unknown kinds and species lie buried in profusion; and my late friend, Professor Barton, of Philadelphia, one of our first transatlantic physiologists, informed me by letter a short time before his death, that they are perpetually turning up skeletons of this description, whose living representatives are no where to be met with.
In few words, every region has been enriched with wonders of animal life that have long been extinct for ever. Where is now that enormous mammoth, whose bulk outrivalled the elephant's ? where that gigantic tapir, of a structure nearly as mountainous, whose huge skeleton has been found in a fossil state in France and Germany; while its only living type, a pigmy of what has departed, exists in the wilds of America? where is now the breathing form of the fossil sloth of America, the magalonix of Cuvier, whose size meted that of the ox ? where the mighty monitor, outstripping the lengthened bulk of the crocodile? itself too, a lord of the ocean, and yet, whose only relics have been traced in the quarries of Maestricht; to which,
† Ser. I, Lect. VI. p. 61.
Stud. of Med. Vol. iv. p. 14. edit. 20, 1825. 1 Ser. II. Lect. II.
as to another leviathan, we may well apply the forcible description of the Book of Job," at whose appearing the mighty were afraid, and who made the deep to boil as a cauldron: who esteemed iron as straw, and brass as rotten wood; who had not his like upon the earth, and was a king amidst the children of pride."*
Over this recondite and bewildering subject skeptics have laughed and critics have puzzled themselves; it is natural history alone that can find us a clue to the labyrinth, that enables us to repose faith in the records of antiquity, and that establishes the important position, that the extravagance of a description is no argument against the truth of a description, and that it is somewhat too much to deny that a thing has existed formerly, for the mere reason that it does not exist now.
*Job xli. 25. 27. 31. 33, 34.
ON ZOOLOGICAL SYSTEMS, AND THE DISTINCTIVE CHARACTERS OF ANIMALS.
WHILE every department of nature displays an unbounded scope to the contemplative mind, a something on which it may perpetually dwell with new and growing delight, and new and growing improvement; we behold in the great division of the animal kingdom a combination of allurements that draw us, and fix us, and fascinate us with a sort of paramount and magical captivity, unknown to either of the other branches of natural history; and which seem to render them chiefly or alone desirable and interesting, in proportion as they relate to animal life. There is, indeed, in the mineral domain, an awe, and a grandeur, and a majesty, irresistibly impressive and sublime; and that cannot fail to lift up the heart to an acknowledgment of the mighty power which piled the massy cliffs upon each other, and rent the mountains asunder, and flung their scattered fragments over the valleys. There is in the realm of vegetables an immeasurable profusion of bounty and of beauty, of every thing that can delight the external eye, and gratify the desire; simple, splendid, variegated, exquisite. But the moment we open the gates of the animal kingdom a new world pours upon us, and a new train of affections take possession of the bosom; it is here, for the first time, that we behold the nice lineaments of feeling, motion, spontaneity; we associate and sympathize with every thing around us, we insensibly acknowledge an approximation (often indeed very remote, but an approximation nevertheless,) to our own nature, and run over with avidity the vast volume that lies before us, of tastes, and customs, and manners, and propensities, and passions, and consummate instincts.
But where shall we commence the perusal of this volume? the different pages of which, though each intrinsically interesting, lie scattered, like the sibyl leaves of antiquity, over every part of the globe, and require to be collected and arranged in order, to give us a just idea of their relative excellence, and to enable us to contemplate them as a whole.
The difficulty has been felt in all ages; and hence multiplied classifications, or schemes for assorting, and grouping into similar divisions, such individuals as indicate a similar structure, or similar habits, or similar powers, have been devised in different periods of the world, and especially in modern times, in which the study of zoology has been pursued with a searching spirit, unknown to the sages of antiquity.-And well has it deserved to be so pursued. "This subject," observes M. Biberg, "is of so much importance, and of such an extent, that if the ablest men were to attempt to treat it thoroughly, an age would pass away before they could explain completely the admirable economy, habits, and structure even of the most